Prevalence and contamination levels of Listeria monocytogenes in retail foods in Japan

Retail foods in Japan were surveyed for the presence and contamination levels of L. monocytogenes. It was isolated from 12.2, 20.6, 37.0 and 25.0% of 41 minced beef, 34 minced pork, 46 minced chicken and 16 minced pork-beef mixture samples, respectively. MPN values were higher than 100/g in five (10.9%) minced chicken samples, but lower than 100/g in all minced beef, pork and pork-beef mixture samples. The organism was also isolated from 5.4% of the 92 smoked salmon samples at MPN values lower than 10/g, and from 3.3% of 213 ready-to-eat raw seafood samples at MPN values from lower than 0.3 to higher than 100/g. None of the 285 vegetable samples were contaminated with L. monocytogenes. These findings indicate that ready-to-eat raw seafoods are relatively high risk among the foods surveyed in this study.     

Incidence of Listeria monocytogenes in different types of meat products on the Belgian retail market

A survey was undertaken to determine the incidence and numbers of L. monocytogenes in a variety of meat products (cooked meat products, raw cured meat products (dried or not), mayonnaise based salads and prepared meals). As expected, raw cured meat products were significantly higher contaminated with L. monocytogenes than cooked meat products, 13.71% (113/824) and 4.90% (167/3405), respectively. Also a larger proportion of raw cured meat product samples contained a high initial level of the pathogen ( > 10 cfu/g). Higher incidence rates were obtained for whole cooked meat products (e.g. cooked ham, bacon) after slicing than before slicing, 6.65 and 1.56%, respectively, indicating cross-contamination. Due to multiple handling and processing steps, the incidence rate of the pathogen was higher for cooked minced meat products than for whole cooked meat products, 6.14 and 3.96%, respectively. No significant differences were obtained in the incidence of L. monocytogenes in whole cured meat products (e.g., raw ham) and minced cured meat products (e.g., dry fermented sausage), 14.92 and 11.69%, respectively. Lower incidence rates of L. monocytogenes were obtained for raw, cured meat products using beef or horse meat, 4.65 and 5.88%, respectively, A high incidence rate of L. monocytogenes was noted for the mayonnaise based salads (21.28% (186/874)) as well as for prepared meals (11.70% (92/786)), the latter especially due to contamination of vegetarian meals.     

Occurrence of pathogens in raw and ready-to-eat meat and poultry products collected from the retail marketplace in Edmonton, Alberta, Canada

A total of 800 meat and poultry products were purchased from the retail marketplace in Edmonton, Alberta, Canada. The products consisted of raw ground beef, chicken legs, pork chops, and ready-to-eat fermented sausage, roast beef, processed turkey breast, chicken wieners, and beef wieners. The samples were analyzed to determine the prevalence of Shiga toxin-producing Escherichia coli, Salmonella, Campylobacter spp., and Listeria monocytogenes. Shiga toxin-producing E. coli 022: H8 was found in one raw ground beef sample. Salmonella and Campylobacter were found in 30 and 62% of raw chicken legs, respectively. L. monocytogenes was found in 52% of raw ground beef, 34% of raw chicken legs, 24% of raw pork chops, 4% of fermented sausages, 3% of processed turkey breast, 5% of beef wieners, and 3% of chicken wieners. The occurrence of pathogens in this study is similar to that in retail products in many other international locales.     

The incidence of Listeria monocytogenes in slaughtered animals, in meat, and in meat products in Yugoslavia

45% of all pigs examined harboured L. monocytogenes in the tonsils, and 3% were faecal excretors. L. monocytogenes was demonstrated in 29% of swabs from the retropharyngeal nodes of cattle and in 19% of faecal samples. The tonsillar and retropharyngeal samples did not correspond to the faecal samples. L. monocytogenes was not demonstrated in the deeper parts of the muscle tissue from 12 beef carcasses all harbouring Listeria in lymph nodes. L. monocytogenes was found in 69% of minced meat (mixed pork and beef) samples. 19% of raw dry sausages and 21% of vacuum-packaged hot smoked sausages were positive for L. monocytogenes. L. monocytogenes was not detected in the hot smoked sausages heated to an internal temperature of 70-75 degrees C, after the smoking process.     

Prevalence and typing of Listeria monocytogenes in ready-to-eat food products on the Belgian market

Listeria monocytogenes is a major concern to producers of ready-to-eat foods because of the high mortality rate associated with listeriosis and the widespread nature of the organism. To investigate the prevalence of this pathogen in different ready-to-eat food products on the Belgian market, a variety of 252 ready-to-eat food products, mainly fish and meat products, were analyzed. Overall, L. monocytogenes was detected in 23.4% of the samples. The highest prevalence of L. monocytogenes was found in prepared minced meat (42.1%) and smoked halibut (33.3%). Contamination levels were in most cases low (<10 CFU/g); however, levels higher than 100 CFU/g were detected in some samples of smoked salmon, smoked halibut, and prepared minced meat. A high prevalence of Listeria innocua (15.8%) and Listeria welshimeri (36.8%) was detected in prepared minced meat. L. monocytogenes strains isolated from different contaminated products were subjected to repetitive element sequence-based PCR (REP-PCR) typing to determine possible associations with product type, producer, or market. REP-PCR patterns were analyzed using BioNumerics software, and seven different groups with at least 90% similarity were identified. The cluster analysis indicates that cross-contamination occurred at the producer and retail level. Serotype identification of the strains by PCR revealed that most belonged to the 1/2a(3a) serotype group.     

Incidence and control of Listeria monocytogenes in foods in Denmark

The Danish regulatory policy on Listeria monocytogenes in foods is based on the principles of HACCP and was developed using a health risk assessment approach. The Danish policy focuses examinations and criteria for L. monocytogenes in ready-to-eat foods and is based on a combination of inspection and product-testing. Based on current epidemiological information from several countries, a concentration of L. monocytogenes not exceeding 100 cfu/g of food at the time of consumption, seems to be of low risk to the consumers. In Denmark, ready-to-eat foods have been placed into six categories where absence of L. monocytogenes in 25 g is required in foods heat treated in the final package and in heat-treated as well as preserved, non heat-treated foods which can support growth within the shelf life. This level is necessary in foods capable of supporting growth, in order not to exceed 100 L. monocytogenes per g at the point of consumption. In heat-treated and preserved foods, which are not supportive of growth within the shelf-life and for raw, ready to eat foods, a level below 10 L. monocytogenes per g is regarded acceptable. A level between 10 and 100 L. monocytogenes per g is not satisfactory and a level above 100/g is not acceptable. Data on the qualitative and quantitative occurrence of L. monocytogenes in foods in Denmark are presented and discussed. In 1997 and 1998, greater than 15,000 samples from different categories of food were examined (semi-quantitatively) for the presence of L. monocytogenes. A significant difference could be seen in the number of samples containing more than 100 L. monocytogenes per g, between different categories of foods (1997, P = 0.001; 1998, P = 0.016). In 1997, preserved meat products and preserved fish products and to a lesser extent vegetables and meat or vegetable mayonnaise were more likely to contain high numbers (i.e. above 100 cfu/g) of L. monocytogenes than other food categories. In 1998, preserved meat products, but also heat-treated meat products, vegetables and meat or vegetable mayonnaise had the highest frequency of samples with > 100 L. monocytogenes per g. In a survey performed in 1994 and 1995, 1.3% of ready-to-eat food samples (heat-treated meat products, preserved meat and fish products) were found to be contaminated with L. monocytogenes at a level above 100 cfu/g. The samples included in this survey were primarily products produced by authorized companies and were comprised mainly of vacuum packed products or products packed in modified atmosphere and with long shelf lives, typically above several weeks. The corresponding percentages of positive samples primarily processed in the retail outlets (heat-treated meat products, preserved meat and fish products) in 1997 and 1998 were 0.3% and 0.6%, respectively. The results suggest that ready-to-eat meat and fish products with extended shelf-lives produced by authorized companies are more likely to contain high numbers (> 100 cfu/g) of L. monocytogenes than products processed in the retail sector which often have a shorter shelf life.     

Prevalence of Listeria monocytogenes and Salmonella in ready-to-eat food in Catalonia, Spain

Listeria monocytogenes and Salmonella are pathogenic bacteria that can contaminate food products during or after processing. Ready-to-eat (RTE) food does not undergo any treatment to ensure its safety before consumption, and therefore risk of foodborne disease must be considered if these pathogens are present in the food. To evaluate the prevalence of these pathogens in RTE food, 140 RTE fish product samples, 501 RTE meat product samples, 462 RTE dairy samples, and 123 RTE dishes and desserts, providing a total of 1,226 samples, were collected from retail stores and food industry and analyzed for the presence of L. monocytogenes. A total of 1,379 samples consisting of 187 RTE fish products and 569 RTE meat products, 484 RTE dairy products, and 139 RTE dishes and desserts were collected and analyzed for the presence of Salmonella. L. monocytogenes was isolated from 20% of frozen Atlantic bonito small pies, 7.9% of smoked salmon samples, 11.1% of the pork luncheon meat samples, 6.2% of frozen chicken croquettes, 16.9% of cured dried sausage samples, 12.5% of cooked ham samples, and 20% of cooked turkey breast samples. L. monocytogenes was also found to be present in 1.3% of fresh salty cheese samples and 15.1% of frozen cannelloni samples. Salmonella was isolated from 1.2% of smoked salmon samples, 1.5% of frozen chicken croquettes, 2% of cooked ham samples, and 11.1% of cured dried sausage samples. Overall, occurrence of these pathogens in RTE foods was similar to that previously reported in the literature.     

Detection, quantification and vitality of Listeria monocytogenes in food as determined by quantitative PCR

In this paper we describe the development of a quantitative PCR (qPCR) technique to detect, quantify and determine the vitality of Listeria monocytogenes in foods. The method was based on the amplification of the intergenic region spacer (IGS) between the 16S and 23S rRNA genes. A panel of more than 100 strains of Listeria spp. and non-Listeria was used in order to verify the specificity of the primers and Taqman probe and amplification signals were obtained only when L. monocytogenes DNA and RNA were loaded in the qPCR mix. Standard curves were constructed in several food matrices (milk, meat, soft cheese, fermented sausage, cured ham and ready-to-eat salad). The quantification limit was of 10(3)-10(4) cfu/g or ml, while for the determination of vitality it was 10(4)-10(5) cfu/g or ml. After an overnight enrichment in BHI at 37 degrees C also 10 cfu/g or ml could be detected in all the matrices used in this study. When we applied the protocol to food samples collected from the market or from small food processing plants, on a total number of 66 samples, 4 fresh cheeses from raw milk gave positive results prior to the overnight incubation, while 9 samples, of which only one represented by fresh meat and the others by cheeses from raw milk, were positive after the enrichment. Out of the 4 positive samples, only one could be quantified and it was determined to contain 4x10(3) cfu/g.     

Random amplified polymorphic DNA typing applied to the study of cross-contamination by Listeria monocytogenes in processed food products

The presence of Listeria spp. was investigated in 369 samples of cooked meat products and 52 of smoked salmon. Incidences of 17.6% for cooked meat and 38.5% for smoked salmon samples were found. All Listeria monocytogenes isolates (34 from meat products and 16 from smoked salmon) were typed serologically and by random amplified polymorphic DNA (RAPD) typing using primers HLWL74 (5'-ACGTATCTGC-3'), HLWL85 (5'-ACAACTGCTC-3'), and OMP-01 (5'-GTI'GGTGGCT-3'). Strains from cooked meat products were characterized and compared in relation to their origin. The detection of identical strains in products of different type and brand packed on the same date suggested cross-contamination, probably during the slicing process. All L monocytogenes isolates from smoked salmon were indistinguishable by serotyping and RAPD, suggesting that this strain was highly disseminated and adapted to the treatment used for the preservation of this food. RAPD subtypes were analyzed using GelCompar version 4.1 software and the unweighted pair method using arithmetic averages, and six groups with at least 78% similarity were established. Serotyping and RAPD results were in concordance, although RAPD showed a higher discriminatory power with L. monocytogenes isolates from meat products. RAPD is an easy method that could be useful to detect cross-contamination occurring during postprocessing manipulations.     

Application of enterocins as biopreservatives against Listeria innocua in meat products

The antilisterial effect of enterocins A and B in meat and meat products (cooked ham, minced pork meat, deboned chicken breasts, paté, and slightly fermented sausages [espetec]) have been shown. An infective dose of 5 to 10 most probable numbers (MPN)/g to simulate the counts of Listeria generally found in meat products was used. Enterocins at 4,800 AU/g reduced the numbers of Listeria innocua by 7.98 log cycles in cooked ham and by 9 log cycles in paté when stored at 7 degrees C for 37 days. In deboned chicken breasts stored at 70 degrees C for 7 days, 4,800 AU/cm2 of enterocins diminished the L. innocua counts in 5.26 log cycles when compared to the control batch. In minced pork meat held at 7 degrees C for up to 6 days, 1,600 AU/g kept L. innocua counts under 3 MPN/g, while the control batch reached 50 CFU/g. In espetec sausages, 648 AU/g diminished the number of L. innocua under 50 CFU/g from the fifth day until the end of the process (12 days) while the control batch kept the initial counts (3 x 104 CFU/g). This is the first report on enterocins showing an antilisterial effect in different types of meat products.     

Use of PFGE typing for tracing contamination with Listeria monocytogenes in three cold-smoked salmon processing plants

The sites of Listeria monocytogenes contamination in three cold-smoked salmon (Salmo salar) processing plants were detected by sampling salmon and the plant's environment and equipment at different production stages. Of the 141 samples collected from three processing plants, 59 (42%) were contaminated with L. monocytogenes. The rates of contamination varied as to the plant and the sample source. L. monocytogenes isolates from 17 various contaminated seafood products (fresh, frozen and smoked fishes, cooked mussels) were also studied. A total of 155 isolates from the three plants and the various seafoods were characterized by genomic macrorestriction using ApaI and SmaI with pulsed-field gel electrophoresis (PFGE) and 82 isolates were serotyped. Macrorestriction yielded 20 pulsotypes and serotyping yielded four serovars: 1/2a, 1/2b, 1/2c, 4b (or e), with 77 (93%) belonging to serovar 1/2a. One clone of L. monocvtogenes predominated and persisted in plant I and was the only pulsotype detected in the final product although it was not isolated from raw salmon. No L. monocytogenes was detected in the smoked skinned salmon processed in plant II, even though 87% of the raw salmon was contaminated. All the smoked salmon samples collected in plant III were contaminated with a unique clone of L. monocytogenes, which may have occurred during slicing. In the three plants, the contamination of final products did not seem to originate from the L. monocytogenes present on raw salmon, but from the processing environment.     

Incidence of Listeria species in seafood and seafood salads

A total of 128 samples of seafood on the Icelandic market were tested for the presence of Listeria monocytogenes and other Listeria species. The samples included raw, smoked and dried fish, frozen shellfish and shrimps as well as several fish salads. These products are generally consumed without heating. Listeria spp. were present in 56% of the samples of raw fish, 29% of the smoked fish, 9% of the shrimps and 32% of the salads. No Listeria spp. were present in the shellfish or dried fish. In 46% of the positive samples L. monocytogenes could be demonstrated, either alone or together with L. innocua. The other positive samples contained L. innocua and, in one sample, L. welshimeri. All products sampled had been processed and packed in Iceland, mostly for use on the domestic market. It is suggested that consuming certain fish products and fish salads may form an additional risk factor for listeriosis in humans.     

High incidence of Listeria monocytogenes in European red smear cheese

The incidence of Listeria and Listeria monocytogenes in European red smear cheese was determined in order to assess whether the lack of recent outbreaks of listeriosis associated with cheese is due to improved hygenic conditions in the dairies. Out of European red-smear cheese samples of various types, 15.8% contained organisms of the genus Listeria, 6.4% of the samples were contaminated with L. monocytogenes, 10.6% with L. innocua, and 1.2% with L. seeligeri. Six cheese samples contained two or more Listeria species, including at least one L. monocytogenes isolate. The incidences of L. monocytogenes in cheeses from various countries were: Italy 17.4%, Germany 9.2%, Austria 10%, and France 3.3%. Listeria were found most frequently in soft and semi-soft cheese. Eight samples contained more than 100 L. monocytogenes cfu/cm2 cheese surface, 2 samples had counts above 10(4) cfu/cm2 cheese surface. Surprisingly, a higher incidence of L. monocytogenes was observed in cheeses made from pasteurized milk (8.0%) than in cheeses manufactured from raw milk (4.8%). Phage-typing of isolated Listeria strains clearly confirmed that (i) contaminations within dairy plants were persistent over a period of several weeks to months and (ii) that cross-contamination within the dairy plant is and important factor. Comparison of our data with past surveys seems to indicate that contamination of red smear soft cheese with L. monocytogenes has not decreased sufficiently over the past 15 years. It is therefore strongly recommended that these products are monitored carefully by cheese-making companies.     

Incidence and characterization of Listeria monocytogenes from domestic and imported foods in Korea

A total of 1,537 domestic and imported food products were examined for the incidence of Listeria monocytogenes between 1993 and 1997 in Korea. L. monocytogenes was detected using the U.S. Department of Agriculture isolation method. Isolated L. monocytogenes was confirmed by polymerase chain reaction with hly1 and hly2 primers designed from the listeriolysin O. Overall, 122 samples (7.9%) contained L. monocytogenes. The rate of isolation was 4.3% for beef, 19.1% for pork, 30.2% for chicken, 1.2% for shellfish, 4.4% for raw milk, 4.4% for frozen smoked mussels, and 6.1% for ice cream. No L. monocytogenes was found in pasteurized milk, pasteurized processed cheese, saltwater fish, dried seafoods, or ham. The overall incidence was lower than that reported in previous studies from other countries. Most isolates were serotype 1/2b except for chicken, in which serotype 1/2a was predominant. The serotyping results might imply the presence of food or geography-specific L. monocytogenes strains.     

Listeria monocytogenes in genussfertigen Lebensmitteln: eine Auswertung der amtlichen Untersuchungen in der Schweiz der Jahre 2006–2008

In the years 2006–2008, 13.978 ready-to-eat foodstuffs were tested by official laboratories of food control in Switzerland for compliance with legal limits for Listeria monocytogenes. Totally, the pathogen could be detected in 67 foods (0,5 % of all samples). Most frequently, raw meat cured sausages (proportion of positive samples 3,9 %) were contaminated followed by smoked fishes (1,4 %) and semi-hard cheeses (1,1 %). For soft cheese, a rather low contamination frequency of 0,3 % was shown. Quantification of L. monocytogenes was possible in 18 ready-to-eat foods from the market and six out of them showed high counts of >1.000 CFU per gram. Concerned were a sandwich with smoked salmon and other components (250.000 CFU/g), smoked salmon (180.000 CFU/g), smoked trout (13.000 CFU/g), semi-hard cheese (9.200 CFU/g) and salami (5.500 and 1.850 CFU/g). In connection with cases of listeriosis, the highest measured count (5 × 10⁷ CFU/ml) was found in liquid cream of a private household where it was probably contaminated and not adequately stored. Surprisingly, in 931 desserts and confectioneries, in 384 ice-creams, in 3.567 pre-cooked foods and in 806 samples of raw fruits or vegetables, L. monocytogenes was never isolated and in 720 delicatessen salads only once (Celery salad with <100 CFU/g). The evaluation of a high number of laboratory data allowed identifying the current focal points of risk, an information which is important for a risk-based design of future control activities.     

The occurrence of Listeria species in milk and dairy products: a national survey in England and Wales

A total of 4172 samples of milk, cheese and other dairy products were examined over a 1-year period for the presence of Listeria species. Strains of Listeria were found most frequently in soft, ripened cows milk cheese; 63 out of 769 (8.2%) samples contained Listeria monocytogenes, 25 samples contained species other than L. monocytogenes, and 18 samples contained both L. monocytogenes and other Listeria spp. Eleven samples of pasteurized cows milk (1.1%) from four dairies contained L. monocytogenes, and other Listeria spp. were isolated from a further five samples. Goats and ewes milk and their products, yogurt, cream and ice cream also occasionally contained Listeria spp. Levels of Listeria were usually low, but 20 samples of cheese contained more than 1000 cfu/g. Most strains of L. monocytogenes belonged to serotype 1/2 (58%) or serotype 4b (33%).     

Prevalence of Listeria monocytogenes in 13 dried sausage processing plants and their products

The aims of the present study were: (i) to investigate the occurrence of Listeria monocytogenes in dried sausage processing plants on surfaces before and during processing, (ii) to study the contamination in meat and sausages at different stages of maturation, (iii) to assess the distribution of L. monocytogenes in the different plants and products studied. Thirteen dried sausage processing plants were sampled at two different times of the working day. The studies were repeated twice to evaluate the persistence of the pathogen. A total of 1029 samples were collected. Among swabbed samples, 15% were positive before the beginning of the working day and 47.3% during working day. Results showed that effectiveness of cleaning and disinfecting operations could be linked with the complexity of processing lines and machines used. The presence of L. monocytogenes in mixed meat amounted to 71.6% of the collected samples. A decrease of the contamination rate in dry sausage was noted, particularly during the drying stage. Nevertheless 3 sausages studied presented a low contamination rate (<3 cfu/g) when ready for consumption. A total of 996 strains of L. monocytogenes were characterised by biochemical tests and serotyping. A majority of isolates were 1/2a (49.5%), 1/2c (19.5%) and 1/2b (13%) strains. A high heterogeneity of serotypes was observed in all plants, raw meat and in sausages during maturation.     

Evaluation of the international reference methods NF EN ISO 11290-1 and 11290-2 and an in-house method for the isolation of Listeria monocytogenes from retail seafood products in france

Retail seafood products were analyzed on their use-by date using the international reference methods NF EN ISO 11290-1 and 11290-2 (collectively method R) or an in-house method (method B) for the isolation of Listeria monocytogenes. The sensitivity of the methods was about 78%. Method R detected more positive samples of smoked salmon and herb-flavored slices of smoked salmon than did method B, whereas the reverse was true for samples of carpaccio-like salmon, herb-flavored slices of raw salmon, and smoked trout. Most products produced a positive result after the first of two enrichments, and little difference was observed after changing the isolation medium (Listeria selective agar, L. monocytogenes blood agar, agar for Listeria according to Ottaviani and Agosti, Oxford agar, and Palcam agar). L. monocytogenes was isolated from 151 (27.8%) of the 543 samples, with concentrations mostly below 100 CFU/g. The pathogen prevalence and concentration in these seafood products varied greatly depending on the producer and the nature of the product. In certain cases, these differences could be explained by problems in cleaning and disinfection operations in the food-processing environment. The identities of L. monocytogenes isolates were confirmed by PCR, and isolates were characterized by random amplification of polymorphic DNA and pulsed-field gel electrophoresis (PFGE). PFGE patterns obtained with the enzymes Apal and AscI produced 26 different pulsotypes. In general, different pulsotypes were present in the different categories of seafood products and were not specific to one producer. The genetic diversity observed in the products was not related to the prevalence found at the manufacturing site. It is therefore important for producers to determine the source(s) of contamination of their product so the risks linked to the presence of L. monocytogenes can be reduced.     

Comparison of two chromogenic media for the detection of Listeria monocytogenes with the plating media recommended by EN/DIN 11290-1

The efficacy of two selective chromogenic culture media, Agar Listeria Ottaviani and Agosti (ALOA) and RAPID' L. mono for the detection of Listeria monocytogenes in food, was compared with that of an official culture method according to the EN/DIN 11290-01 and -02 protocols [corresponding to the section 35 LMBG (German Food Act) method]. A total of 310 pre-packed ready-to-eat food samples (100 of graved and cold smoked salmon, 130 of different raw and cooked sausages and 80 of delicatessen and mixed salads) were examined. L. monocytogenes was identified in 52 investigated salmon samples. Using two chromogenic media, 50 samples were found positive for L. monocytogenes. Compared to the reference method there were no false-positive results. By the EN/DIN 11290-01 culture procedure after the selective enrichment in Fraser broth 12 out of 130 samples of sausages were positive for L. monocytogenes. These 12 samples were also positive for L. monocytogenes with the chromogenic medium RAPID' L. mono. One sample was false negative with ALOA. Three additional samples were found positive with ALOA and four with RAPID' L. mono. The standard method was inadequate to confirm these samples as positive. Listeria spp. were isolated from 7 samples of mixed salads with both methods. One, 3 and 3 samples were found to contain L. monocytogenes, L. innocua and L. seeligeri, respectively. Both chromogenic media enabled a rapid and specific detection of L. monocytogenes within 24h after enrichment. Visual detection of pathogenic L. monocytogenes and other Listeria spp. was easier on chromogenic media.     

Comparison of a cold enrichment and the FDA method for isolating Listeria monocytogenes and other Listeria spp. from ready-to-eat food on retail sale in the U.K

A cold enrichment and the modified FDA selective enrichment method were compared for their ability to detect Listeria monocytogenes and other Listeria species from various ready-to-eat foods on sale in the UK. Of 57 food samples examined using cold enrichment, five yielded L. monocytogenes, and two L. innocua. The FDA enrichment method yielded three samples positive for L. monocytogenes only. Foods examined included soft cheeses, fermented meat sausages, pates and salads.